TextField does not pass disabled status to InputLabel & FormHelperText

[WreckedArrow]

• This is a v1.x issue.
• I have searched the issues of this repository and believe that this is not a duplicate.

Expected Behavior

Passing the disabled prop to a TextField should also apply the disabled style to the label and helper text.

Current Behavior

Only the Input component is disabled.

Steps to Reproduce

Link: https://codesandbox.io/s/403p55597

1. Create a TextField and pass it the disabled prop.
2. Wrap an Input, InputLabel, and FormHelperText in a FormControl, and pass it the disabled prop.
3. The TextField's label and helper text will not have the disabled style.

Context

It's a minor issue since the disabled prop can be manually passed within the TextField using InputLabelProps, etc., but I found the current behavior surprising. In the source, I believe the disabled prop should be given to FormControl like the error and required props, unless there is some need to isolate disabled to only the Input.

[oliviertassinari]

@WreckedArrow Well spotted, we should be able to fix the issue by removing the special handling of the disabled property in the TextField component.
https://github.com/mui-org/material-ui/blob/f21551ec742e99871177d9ef998a183e1b5e3933/packages/material-ui/src/TextField/TextField.js#L85

Do you want to work on it? :)